A comparative study: The effect of surface treatments on the tribological properties of Ti–6Al–4V alloy (original) (raw)
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The Effect of Low Temperature Plasma Nitriding on Wear Resistance of Ti6Al4V Alloy
Acta Physica Polonica A, 2014
The eect of low temperature plasma nitriding on wear resistance of Ti6Al4V alloy were investigated. There have been several studies to investigate the low temperature plasma nitriding on Ti6Al4V alloy. Plasma nitriding processes under gas mixture of N2/H2 = 3 were performed at temperature 535 • C for duration of 4, 8 and 12 h. Adhesive wear tests were carried out by using a tribometer in block-on-ring conguration (ASTM G77), in sliding conditions, without lubricants and in air. Surface hardness of the plasma nitrided samples were measured by a Vickers hardness tester machine. Scanning electron microscopy studies were conducted to understand the wear mechanisms involved during the adhesive wear. Wear rate was calculated using weight loss per unit sliding distance. It was found that the wear resistance and surface hardness of the alloy improved considerably after plasma nitriding process. The wear resistance of the plasma nitrided samples were higher than of the unnitrided samples. Extension of nitriding times from 4 h to 12 h in the Ti6Al4V alloy improved remerkably the wear resistance and surface hardness.
Improving the tribological properties of Ti–6Al–4V alloy by nitrogen-ion implantation
Surface and Coatings Technology, 1999
Ti-doped diamond like carbon films were deposited on both untreated and plasma nitrided Ti6Al4V alloy using Closed Field Unbalanced Magnetron Sputtering (CFUMBS) method and their tribological properties were evaluated by conducting sliding wear conditions. The influence of the nitrided layer on tribological behavior of Ti-DLC films was studied by means of XRD, SEM, scratch tester, microhardness tester and pin-ondisc tribotester. The microhardness results pointed out that the duplex treatment dramatically increased the surface hardness and reduced the plastic deformation of the alloy. Wear tests showed that Ti-DLC coatings on both untreated and nitrided surfaces caused a reduction in the coefficient of friction. The reason of the reduction in the coefficient of friction was found to be the formation of transfer film between the sliding surfaces. Wear rates demonstrated that wear resistance of duplex treated (Ti-DLC coating after nitriding) Ti6Al4V alloy was significantly improved.
Nano- and micro-tribological behaviours of plasma nitrided Ti6Al4V alloys
Journal of the Mechanical Behavior of Biomedical Materials, 2017
Plasma nitriding of the Ti-6Al-4V alloy (TA) sample was carried out in a plasma reactor with a hot wall vacuum chamber. For ease of comparison these plasma nitrided samples were termed as TAPN. The TA and TAPN samples were characterized by XRD, Optical microscopy, FESEM, TEM, EDX, AFM, nanoindentation, micro scratch, nanotribology, sliding wear resistance evaluation and in vitro cytotoxicity evaluation techniques. The experimental results confirmed that the nanohardness, Young's modulus, micro scratch wear resistance, nanowear resistance, sliding wear resistance of the TAPN samples were much better than those of the TA samples. Further, when the data are normalized with respect to those of the TA alloy, the TAPN sample showed cell viability about 11% higher than that of the TA alloy used in the present work. This happened due to the formation of a surface hardened embedded nitrided metallic alloy layer zone (ENMALZ) having a finer microstructure characterized by presence of hard ceramic Ti 2 N, TiN etc. phases in the TAPN samples, which could find enhanced application as a bioimplant material.
Tribological properties of duplex plasma oxidised, nitrided and PVD coated Ti–6Al–4V
Surface and Coatings Technology, 2011
Sequential triode plasma oxidation and nitriding have been used to provide enhanced load support for physical vapour deposited (PVD) hard coatings. The diffusion process has been designed to maximise process efficiency and coating adhesion, thereby significantly improving the tribological properties of the Ti-6Al-4V alloyparticularly at high contact pressures. This has been demonstrated using unlubricated linear reciprocating-sliding ball-on-plate wear tests and micro-scratch adhesion testing. Also, surface microprofilometry, nano/micro-indentation hardness testing, scanning electron microscopy (SEM), energydispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and glow-discharge optical emission spectroscopy (GDOES) data are presented to corroborate the effect of the several plasma diffusion processes and duplex diffusion/coating combinations discussed here. The results presented show that the novel processing technique developed permits the use of oxygen diffusion in order to obtain relatively large case depths in shorter treatment times without compromising the adhesion strength of subsequently deposited PVD layers.
Surface modification of Ti–6Al–4V alloys using triode plasma oxidation treatments
Surface and Coatings Technology, 2012
In this study, triode plasma oxidation (TPO) has been used to improve the tribological characteristics of Ti-6Al-4V. The effect of TPO on ball-on-plate reciprocating-sliding, impact, and micro-abrasion wear resistance of this alloy is investigated. Surface micro-profilometry, nano-/micro-indentation hardness testing, scratch-adhesion testing, scanning electron microscopy (SEM), atomic force microscopy (AFM), glancing-angle X-ray diffraction (GAXRD), and glow-discharge optical emission spectroscopy (GDOES) data is presented to corroborate the effects of the oxidation process. 'Traditional' thermal oxidation processes were used to benchmark this novel treatment. Following TPO treatment at 700°C for only 4 h, a hard (exceeding 11 GPa) and well-adhered oxide layer, composed of mixtures of the anatase and rutile polymorphs of TiO 2 , was formed at the surface of the Ti-alloy. This layer is accompanied by a much larger oxygen-solution strengthened zone which creates a gradual chemical and mechanical gradient from the hard oxide 'compound layer' into the ductile substrate core. The various wear testing methods employed revealed excellent wear resistance of the TPO-treated alloy-compared both to the untreated alloy and to conventional, thermally oxidised samples.
Surface engineering to improve the durability and lubricity of Ti-6Al-4V alloy
Wear, 2011
The fuel efficiency of ground vehicles, like heavy trucks, can be improved by reducing engine weight. While primarily known for its use in aerospace structures, titanium alloy Ti-6Al-4V has the potential to replace heavier steel in certain friction and wear-critical diesel engine components like connecting rods, intake valves, movable turbocharger vanes, and pistons. While Ti-6Al-4V exhibits excellent corrosion resistance, good fatigue strength, and acceptable fracture toughness, it has poor sliding characteristics. Titanium alloys have a propensity to fail by galling, and often exhibit high and unstable friction coefficients. In the current work, selected surface engineering techniques were compared to determine which best enhance the tribological performance of Ti-6Al-4V alloy and another alloy, 60Ni-40Ti. Candidate treatments included diffusion treatments, hard coatings (TiN and CrN), a soft coating (Cu-Ni-In), titanium-matrix TiB 2 in situ-formed composite, and shot peening. Diffusion treatments included oxygen diffusion, nitriding, and carburizing. In addition to studying the effects of individual surface engineering approaches, some were combined in an attempt to maximize their effects, but at the same time retain the mechanical properties of the titanium alloy achieved by proper heat treatment. Both dry and lubricated friction and wear tests were conducted using ASTM G133 (linearly reciprocating ball-on-flat). The ball specimens were AISI 52100 bearing steel. Lubricated tests were performed in engine-conditioned diesel engine oil. Test coupons were characterized using microindentation, stylus and optical interferometry, and metallographic examination. Surface engineering methods significantly improved the wear performance of Ti-6Al-4V alloy, but their relative rankings varied significantly between oil-lubricated and non-lubricated conditions.
Surface & Coatings Technology, 2008
The microstructure, mechanical and tribological properties of composite intermetallic layers of the Ti-Al system were investigated. The layers on the two-phase (α + β) Ti6Al4V titanium alloy were obtained using the hybrid method, which consist of two stages. First, the titanium alloy was covered with aluminum layer by magnetron sputtering. In the second stage, coated specimens were treated under glow discharge conditions. The surface treatment makes it possible to obtain the diffusional composite layers which considerably improve the mechanical and wear resistance properties of the material. These properties cannot be achieved using simple methods of surface engineering. The chemical and phase composition of the composite intermetallic layers was investigated. It has been shown that the hybrid method significantly increases the hardness and wear resistance of the titanium alloy and can widen the range of application of the material. Because of the diffusional character of the intermetallic layers they possess good adhesion to the titanium substrate.
Effect of Surface Treatment on Tribological Behavior of Ti-6Al-4V Implant Alloy
Journal of Minerals and Materials Characterization and Engineering, 2012
Titanium alloys are extensively used in various fields of engineering, medicine, aerospace, marine due to its excellent mechanical properties. Its usage is more pronounced today in the field of biomedical implants due to its superior biocompatibility, corrosive resistance and high strength to weight ratio. It has poor abrasive wear resistance due to high coefficient of friction and low thermal conductivity. Poor abrasive wear resistance results in the formation of wear debris at the implant area causing toxicity, inflammation and pain. Surface treatment of the implant alloy through heat treatment, application of protective coatings, introduction of compressive residual stresses by shotpeening and shot blasting are some of the methods to mitigate wear of the implant alloy. In this work Ti-6Al-4V implant alloy is treated under various conditions of heat treatment, shotpeening and shot blasting operations on a pin on disc wear testing machine. Shotpeening and Shot blasting are the operations usually performed on this alloy to improve fatigue strength and surface roughness. In this work the effect of above surface treatments were studied on the wear behavior of Ti-6Al-4V implant alloy and an improvement in the wear resistance of the alloy is reported. Scanning Electron micrograph (SEM) along with Energy Dispersive Spectrometry analysis (EDS) is done to authenticate the experimental results obtained during the wear testing procedure.
Plasma nitriding behavior of Ti6Al4V orthopedic alloy
Surface and Coatings Technology, 2008
The influence of plasma nitriding on mechanical, corrosion and tribological properties of Ti6Al4V has been investigated using X-ray diffraction, microhardness tester, scanning electron microscopy, pin-on-disc tribotester, electrochemical polarization and impedance spectroscopy. Plasma nitriding treatment of Ti6Al4V has been performed in 25%Ar-75%N 2 gas mixture, for treatment times of 1-4 h at the temperatures of 650-750°C. The corrosion tests were carried out in Ringer solution at 37°C, and the wear tests were performed in dry sliding conditions. XRD analyses confirm the formation of δ-TiN and tetragonal ɛ-Ti 2 N phases in the modified layer. It was observed that the surface hardness and wear resistance increase as the treatment time and temperature increase. The electrochemical impedance measurements indicate a decrease in double layer capacitance value and increase in charge transfer resistance for the nitrided specimens compared to the untreated ones.
Tribological behaviors of Ti–6Al–4V modified by chemical methods
Tribology International, 2010
In order to improve the tribological properties of titanium-based implants, sodium hydroxide (NaOH), hydrogen peroxide (H 2 O 2 ) solutions, sol-gel hydroxyapatite (HA) film, thermal treatment and combined methods of NaOH solution/HA film, H 2 O 2 solution/HA film are used to modify the surfaces of Ti-6Al-4V (coded TC4). The chemical states of some typical elements in the modified surfaces were detected by means of X-ray photoelectron spectroscopy (XPS). The tribological properties of modified surfaces sliding against an AISI52100 steel ball were evaluated on a reciprocating friction and wear tester. As the results, complex surfaces with varied components are obtained. All the methods are effective in improving the wear resistance of Ti-6Al-4V in different degrees. Among all, the surface modified by the combined method of NaOH solution/HA film gives the best tribological performances. The friction coefficient is also greatly reduced by the modification of NaOH solution. The order of the wear resistance under 3 N is as following: Ti-NaOH-HA4Ti-NaOH4Ti-HA4Ti-H 2 O 2 -HA4Ti-H 2 O 2 4Ti-500; under 1 N is Ti-HA, Ti-NaOH-HA4Ti-NaOH. For Ti-H 2 O 2 , a very low friction coefficient and long wear life over 2000 passes is obtained under 1 N. SEM observation of the morphologies of worn surfaces indicates that the wear of TC4 is characteristic of abrasive wear. Differently, abrasion, plastic deformation and micro-crack dominate the wear of Ti-HA; slight abrasive wear dominate the wear mechanism of Ti-NaOH and microfracture and abrasive wear for Ti-NaOH-HA and Ti-H 2 O 2 -HA, while the sample modified by thermal treatment is characterized by sever fracture. The superior friction reduction and wear resistance of HA films are greatly attributed to the slight plastic deformation of the film. NaOH solution is superior in improving the wear resistance and decreasing the friction coefficient under relative higher load (3 N) and H 2 O 2 is helpful to reduce friction and wear under relatively lower load (1 N). Combined method of Ti-NaOH-HA is suggested to improve the wear resistance of Ti-6Al-4V for medial applications under fretting situations.